The PCA9901 is a 20 mA current source for a single LED that allows stand-alone blinking of a predefined pattern to off-load the microcontroller and save battery power.
Programming of the device is done through a training sequence: the host controller sends the LED lighting sequence and the PCA9901 memorizes it. Once the sequence has been memorized, the PCA9901 can be programmed to send it once or in a loop until the host controller requests the sequence to be stopped.
Commands and blinking sequence are sent through a uni-directional one-wire interface. Commands include: Training Start, Training End, Execute Sequence (once or in loop until a Stop Command is requested) and Reset. A blinking sequence includes up to 3 different blinking patterns, each defined by its ON and OFF timings.
A bypass mode allows the training sequence to be ignored and the LED output to follow the one-wire interface Logic state to directly control the LED from the microcontroller.
An external resistor sets the maximum current that flows in the LED, which can be set between 1 mA and 20 mA.
The PCA9901 operates from a 2.7 V to 5.5 V power supply.